1. Field of the Invention
The present invention relates to abrasion resistant ferro-based sintered alloy for use as abrasion resistant members of internal combustion engines, more particularly, those members which require thermal resistance, corrosion resistance and abrasion resistance simultaneously such as valve seats, valves, etc. and other slidable members.
2. Description of the Prior Art
Conventional abrasion resistant ferro-based sintered alloys comprise various carbides and alloy particles dispersed in pearlite or martensite matrix or substrate or those treated by lead impregnation, sulfur impregnation or steam treatment to improve abrasion resistance and compatibility with other members with which they are employed in a slidable contact.
These materials comprise various elements introduced in large amounts in a form of alloy powder, powder mixture or single powder of the elements. The addition of the elements often causes a problem since these elements, in particular cobalt, are available only with difficulty.
Further, members to be used under the conditions of high temperatures and high loads tend to suffer various drawbacks, for example, lead will be fused and flow out when the alloy impregnated with lead is used, the hardness of those members subjected to steam treatment will be too high and the material will become brittle. In addition, productivity is decreased by the addition of production steps when such treatments are effected.
It is, therefore, strongly desired that alloy comprising as small as possible an amount of useful additive elements but exhibiting excellent thermal resistance, corrosion resistance and abrasion resistance be developed to thereby save natural resources as well as improve productivity.